1. Field of the Invention
The present invention relates to an optical apparatus including a so-called ball-guide image-stabilizing unit.
2. Description of the Related Art
The ball-guide image-stabilizing unit to be installed in an interchangeable lens or a video camera has been disclosed in Japanese Patent Laid-Open No. H10-319465, for instance. To be more precise, multiple balls are sandwiched between a base member of the image-stabilizing unit and a movable unit including an image stabilization lens by using a spring force so as to guide the movable unit in a plane orthogonal to the optical axis by rolling motions of the balls. It is possible, by this configuration, to realize the image-stabilizing unit of which drive resistance is reduced while blocking displacement of the movable unit in the optical axis direction.
As for the ball-guide image-stabilizing unit, however, it is desirable that the balls be placed at initial positions which are at the center of a range of movement thereof or in the vicinity thereof before starting an image stabilization operation. The image-stabilizing unit of Japanese Patent Laid-Open No. H10-319465 has the balls housed in a concave portion for limiting the range of movement formed on the base member. And in a state where the balls have moved greatly from the initial positions and are in contact with a sidewall surface of the concave portion, the balls hardly roll due to friction with the sidewall surface. Thus, drive resistance of the movable unit increases. In many cases, such a deviation of the balls from the initial positions occurs when an impact is brought on a lens apparatus.
For this reason, Japanese Patent Laid-Open No. 2001-290184 and Japanese Patent Laid-Open No. 2002-196382 have disclosed a technique of, before causing the ball-guide image-stabilizing unit to perform an image stabilization operation, causing it to perform an initializing operation of driving the movable unit to mechanical ends in two mutually orthogonal directions, that is, vertical and horizontal directions, and then returning it to a movable center position. It is thereby possible to reset the balls at the initial positions of the range of movement whatever positions in the range of movement the balls are initially at.
Japanese Patent Laid-Open No. 2002-196382 has proposed that the initializing operation of ball positions should be performed subsequently to or simultaneously with a reset operation of zooming or focusing at the time of power-on. It also proposes the initializing operation should be performed in a state other than during use of an image-pickup apparatus (during monitor observation of a picked up image or recording thereof).
In the case where a photographer observes a subject through a finder in real time as with a single-lens reflex camera system, displacement of a subject image due to the initializing operation is observed if the initializing operation of the ball positions is performed during observation of the finder. Therefore, there is a possibility of giving the photographer a sense of discomfort.
Even if the initializing operation is performed in a state other than using an image-pickup apparatus, there is a possibility that the ball positions deviate from the initial positions due to an impact during the use or the like after the power-on of the image-pickup apparatus.